Like he said. The higher the octane the harder the fuel is to spark and combustion to take place
with you're set up try the different fuels and see if they benefit any better than the last
the higher octanes are made to withstand the heat and pressure inside the cylinder so that pre-ignition doesn't take pplace once you get pre-ignition the fuel on the upstroke will collide with the fuel ignited from the spark plug and that leads to detonation which will destroy your motor very quick
if you've been running 90 octane this long then you should be fine
if you can, get a borescope or little camera to look inside your cylinders for wear
hopefully that helps a little
